1. The Field of the Invention
The present invention relates to a syringe apparatus for dispensing compositions particularly viscous dental compositions. More particularly, the present invention is directed to syringes which enable compositions to be viscous compositions to be easily delivered.
2. The Relevant Technology
Three syringes are described below to provide an understanding of different plunger configurations which may be utilized with different materials. Syringe 106, depicted in FIGS. 1A-1C, is an example of a widely used conventional syringe. Syringe 10 can be used with both high and low viscosity fluids. Syringe 100 depicted in FIGS. 2A-2C is more useful with high viscosity fluids due to the configuration of the tip 160 of plunger 150. Another syringe is shown in FIGS. 3A-3C at 200.
The primary components of syringe 10 are a barrel 20 and a plunger 50 which is slidably engaged in barrel 20. Note that plunger 50 has a cylindrically shaped sealing gasket 60 made of a soft, compressible, sealing material, such as rubber, which allows the exterior surface of gasket 60 to seal against barrel 20 to ensure that the fluids held within barrel 20 do not leak.
Although syringe 10 is shown primarily to depict sealing gasket 60, the other features of syringe 10 are described in detail hereinbelow in order to appreciate certain limitations of syringes such as syringe 10. Note also that all of the syringes shown herein, including those shown in FIGS. 2A-2C, 3A-3C, 4A-4C and 5A-5C, are depicted with barrel 20. Accordingly, the features of barrel 20 are not numbered or described in detail in reference to syringes 100, 200 or 300.
Barrel 20 has a top grasping end 21 opposite a bottom end 29 with a substantially cylindrical sidewall 22 extending therebetween. Sidewall 22 has an exterior surface 23 and an interior surface 24. Interior surface 24 defines a substantially cylindrical or tubular chamber 25 for holding a composition. Chambers such as chamber 25 of barrel 20 are typically configured to hold about 1.2 cc of liquid.
Barrel 20 has a grasping handle 26 which is an annular flange extending radially outward from sidewall 22 at top grasping end 21 of barrel 20. Grasping handle 26 is centrally located around opening 27 which has the same diameter as the interior surface 24 of chamber 25.
A radial extension 28 extends integrally from sidewall 22 at bottom end 29 inward to define an exit port 32. Radial extension 28 acts as a stop for plunger 50 as plunger 50 is depressed.
Exit port 32 is the opening into channel 33 which enables channel 33 to communicate with chamber 25. Note that channel 33 is the interior surface of tapered exit tube 30. Channel 33 extends through tapered exit tube 30 and terminates at outlet 34.
Surrounding exit tube 30 is an attachment sleeve 36. Attachment sleeve 36 has an interior surface 37 with engagement threads 38 positioned thereon. A nozzle or tip 40, shown in FIG. 1C, may be selectively attached to barrel 20 by coupling with threads 38. A variety of tips are available which may be attached such that channel 33 of exit tube 30 is in fluid communication with the tip for guided delivery of the composition to a desired location.
Tip 40 is configured to selectively attach in fluid communication with exit tube 30. To accomplish this end, tip 40 has a threaded end 42 for engagement with threads 38 of attachment sleeve 36. Opposite threaded end 42 is a flexible and angled spout 44 for guiding delivery of the composition to a desired location. It is of course envisioned that different sizes and shapes of spouts 44 can be used depending on the type and intended use of the composition. Furthermore, in alternative embodiments, tip 40 may be permanently attached to bottom end 29 or means other than threads may be used to attach different sizes and/or shapes of tips.
Plunger 50 has a distal lead end 51 opposite from a proximal pushing end 53 with a stem 52 extending therebetween. Radially extending outward at pushing end 53 is an annular pushing handle 58 used in advancing plunger 50. Plunger 50 is sized to be slidably received within chamber 25 through opening 27 at top grasping end 21. Plunger 50 has a length that permits it to be advanced to bottom end 29 such that a small portion of plunger 50 remains extending beyond opening 27. FIG. 1C depicts a loaded syringe with only gasket 60 and a portion of stem 52 in chamber 25 of barrel 20. In use, plunger 50 is depressed further and further into chamber 25 until gasket 60 contacts radial extension 28 to stop the depression of plunger 50.
Cylindrically shaped sealing gasket 60 is positioned at lead end 51 of plunger 50. More particularly, gasket 60 is coupled to stem 52 via a gasket holder as shown in FIG. 1B at 64. As indicated above, gasket 60 is made of a soft, compressible, sealing material, such as rubber, which allows the exterior surface of gasket 60 to seal against interior surface 24 of chamber 25 as plunger 50 is advanced within chamber 25 or selectively slid down to bottom end 29. While syringe 10 can be utilized to deliver either high or low viscosity fluids, the sealing capability of gasket 60 enables it to be particularly useful with low viscosity fluids as it prevents rapid evaporation of such fluids.
Gasket holder 64 has a post 66 with a head element 65 integrally extending at one end and a base 67 integrally extending from the other end. Head element 65 and post 66 are inserted into an opening 62 of gasket 60 which expands such that head element 65 can be inserted therein and then elastically return to its original size such that head element 65 is removably held in gasket 60. Base 67 is connected to stem 52 to hold gasket holder 64 in position.
Syringe 100 shown in FIGS. 2A-2C has a plunger 150 which is less expensive to manufacture than plunger 50 as plunger 150 is integrally made from a single material. Syringe 100 is similar to the syringes disclosed in U.S. Pat. No. 4,986,820 which is hereby incorporated by reference. U.S. Pat. No. 4,986,820, which is entitled xe2x80x9cSyringe Apparatus Having Improved Plungerxe2x80x9d, issued to Dan E. Fischer and is owned by Ultradent Products, Inc.
Like plunger 50, plunger 150 has a pushing handle 158 and a stem 152 extending between a distal lead end 151 and a pushing end 153. The plunger tip configuration located at distal lead end 152, however, is distinct from that of plunger 50. The tip 160 has a conical or bowl-shaped rim 162 which is separated by a rim notch 164 from a ring 166. A ring notch 168 is located between ring 166 and stem 152.
Conical rim 162 has a diameter identified in FIG. 2C as DR which is slightly greater than the diameter of the interior surface 24 of barrel 20 identified in FIG. 2C as DB. Since the diameter of conical rim 162, DR, is slightly greater than the diameter of the interior surface 24 of barrel 20, DB, conical rim 162 provides a fluid tight seal with interior surface 24 of barrel 20. Ring 166 provides a secondary seal with interior surface 24 of barrel 20.
Rim notch 164 and ring notch 168 combined with the material properties, thickness is of conical rim 162, and physical dimensions such as length, angular orientation, etc. all combined to enable conical rim 162 and ring 166 an appropriate amount of flexibility. An advantage of this configuration as stated in U.S. Pat. No. 4,986,820 at column 6, line 33-39 is that when a user increases pressure on the plunger, such as when a particularly viscous formulation is contained with barrel 20, the conical shape of rim 162 causes the rim to be pressed against interior surface 24 of barrel 20 with even greater force, thus ensuring an adequate seal.
Although, the tip configuration of plunger 150 typically enables the composition contained in chamber 25 to be dispensed at a uniform rate and in a controlled manner, variations may occur. More particularly, as plunger 150 is depressed it may suddenly slip in barrel 20 and then stop such that the contents of the barrel are delivered more rapidly than desired. This can potentially result in delivery of excessive amounts of a composition which the practitioner is attempting to deliver in a discrete amount. When a plunger encounters less resistance and slips forward within a barrel, it may slip and then stop several times before the user is able to adjust the amount of pressure that is being applied. Encountering suddenly varied resistance to yield rapid forward movement and then abrupt stopping of a plunger within a barrel is referred to as a xe2x80x9cchatteringxe2x80x9d effect.
Chattering can occur when delivering high viscosity fluids with syringe 100 since conical rim 162 presses more firmly against interior surface 24 of barrel 20 with such fluids due to the force required to push such fluids. More particularly, the flexible configuration of conical rim 162 causes contact surface 163 of rim 164 to press against sidewall 22 of chamber 25 in manner which can result in variations. Contact surface 163 is shown in FIG. 2C to be rather sharp and thin which can result in either excessive flexibility or a tendency to create excessive friction. While the rim is shown in FIG. 5 of U.S. Pat. No. 4,986,820 to be thicker than is shown in FIG. 2C and the contact surface is not shown to be as sharp in FIG. 5 of U.S. Pat. No. 4,986,820 as in FIG. 2C, the tendency to chatter is quite similar. So while the flexibility of conical rim 164 and the conical rim disclosed in U.S. Pat. No. 4,986,820 provides flexibility that forms a useful seal, this same flexibility can have an undesirable result when combined with the friction caused by the contact surface of the of the conical rim.
Another disadvantage of syringes such as syringe 100 is that if any imperfections occur to the contact surface 163, then the ability of conical rim 162 to form a seal with interior surface 24 of barrel 20 can be impaired. This can enable the contents of barrel 20 to evaporate. Also, if an imperfection occurs in conical rim at contact surface 163, the likelihood of chattering is further increased which may result in the contents of barrel 20 being unusable. The occurrence of such imperfections is increased by the thinness of conical rim 163 and sharpness of contact surface 163 which requires very exact formations.
Syringe 200 shown in FIGS. 3A-3C is another example of a plunger with an integral plunger tip. Like plunger 50 and plunger 150, plunger 250 has a pushing handle 258 and a stem 252 extending between a distal lead end 251 and a pushing end 253. Stem 252 has solid cross-shaped cross-section to minimize contact with interior surface 24 of barrel 20. Also such solid cross-shaped stems can be formed from less plastic than the hollow round stems such as those shown at 52 and 152. However, such solid cross-shaped stem configurations are not as strong as hollow round stems. Note that in addition to having an integral tip 260, plunger 250 also has an evacuator 290 integrally extending from tip 260 for mated insertion into channel 33 of exit tube 30.
As indicated above, the plunger tip configuration located at distal lead end 152 is distinct from that of the other plungers. Stem 252 tapers to a neck 262 which then flares outward to a solid tip body 264. Solid tip body has a back end 265 and a front end 266. Evacuator 290 extends from the center of the front end 266 of solid tip body 264. Solid tip body 264 has a radial notch 268 formed into its front end 266 around its perimeter such that a rigid arm 270 extends upward toward front end 266.
Solid tip body 264 is integrally connected with the base of arm 270. Arm 270 has a thick portion 272 which includes its base and a bulge ring 274 which is a round protuberance extending radially around arm 270. Arm 270 also has a thin flash portion 276 which extends integrally from thick portion 274 at bulge ring 272 and terminates at a distal end 278. Arm 270 has a length such that distal end 278 extends no farther than front end 266 of solid tip body 264.
Bulge ring 274 has a diameter identified in FIG. 3C as DR which is slightly greater than the diameter of the interior surface 24 of barrel 20 identified in FIG. 3C as DB. Since the diameter of bulge ring 274, DR, is slightly greater than the diameter of the interior surface 24 of barrel 20, DB, bulge ring 274 provides a fluid tight seal with interior surface 24 of barrel 20. While barrel 20 used with plunger 250 appears as it does in the figures depicting syringes 10 and 100, barrel 20 used with plunger 250 is actually not identical. When paired with plunger 250, barrel 20 is formed from a more flexible plastic than is used to form the barrel paired with plungers 50 and 150 or barrel 20 is formed such that the diameter of the interior surface 24 is slightly thinner. The relative flexibility or narrow inner diameter of the barrel 20 enables bulge ring 274 to actually push out the sidewalls of the barrel 20, as shown in FIG. 3C at FR. In fact, when one grasps barrel 20 as plunger 250 is moved within barrel 20 one can actually feel bulge ring 274 pass through the barrel 20 due to the diameter of bulge ring 274 and the stiffness of arm 270.
The rigidness of arm 270 and the diameter of bulge ring 274 are important features to the ability of the plunger tip 260 to form a seal with interior surface 24 of barrel 20. This rigidness is achieved through several features of plunger tip 260 including: the configuration of solid tip body 264 and the length and thickness of thick portion 272 of arm 270. Solid body tip 264 ensures that tip 264 arm 270 can be firmly pushed against interior surface 24 of barrel 20. The thickness and length of thick portion 272 enable bulge ring 274 to be effective in creating a seal as it is adequately short and thick enough to maintain pressure against interior surface 24 without flexing inward. To better appreciate these features, it should be understood that thick portion 272 terminates after bulge ring 274 and arm 270 then tapers in thickness thereafter to that of flash portion 276. Accordingly, the length of thick portion 272 of arm 270 is such that it extends only slightly above the base 269 of notch 268. This length of thick portion 272 relative to the base 269 of notch 268 limits its flexibility and enables it to be sufficiently stiff to push against interior surface 24.
The exterior side arm 270 curves inward at flash portion 276 while the interior side of arm 272 which is the outer side of notch 268 is relatively straight. Since arm 270 dramatically tapers in thickness from thick portion 272 to a flash portion 276 and curves inward beginning at bulge ring 274, flash portion 276 is not in contact with interior surface 24 of barrel 20. Note that since the thickness of arm 270 transitions so abruptly from that of bulge ring 274 to that of flash portion 276, there is a ridge 275 on the exterior side of arm 272. Flash portion 276 continues to taper up to distal end 278 which is very thin and flexible. The taper in thickness at ridge 275 is so pronounced that flash portion 276 can flex at ridge 275 and it prevents rigid arm 270 from moving in any other section.
Since the rigidity and thickness of thick portion 272 combined with the diameter of bulge ring 274 enable a seal to be formed between bulge ring 274 and interior surface 24 of barrel 20, flash portion 276 has no function during storage. When tip 260 of plunger 250 is urged against the contents of barrel 20, it appears flash portion 276 also makes no contribution. More particularly, since bulge ring 274 extends out so far and since flash portion is inset with respect to interior surface 24 of barrel 20, it is difficult for flash portion to even contact interior surface 24. Further since flash portion extends integrally from thick portion 272, the rigidity of thick portion limits the movement of flash portion 276. Flash portion 276 is itself very flexible due to its thinness, however, it is also relatively short. The length of flash portion 276 is particularly limiting in light of manner in which flash portion 276 is inset from interior surface 24 of barrel 20. Further even if flash portion 276 is able to contact interior surface 24 of barrel 20 it is unlikely to have any effect due to the thinness and flexibility of flash portion 276.
While the rigidity and shortness of thick portion 272 enables it to be sufficiently stiff to push against interior surface 24, its limited flexibility requires that barrel 20 be designed to accommodate bulge ring 274 of thick portion 272. The configuration of plunger tip 260 may also prevent syringe 200 from being useful for the delivery of certain compositions.
In conclusion, a syringe is needed which enables a user to deliver a composition in a highly controlled manner, particularly viscous compositions. Additionally, a syringe is needed which has a plunger with an integral tip adapted to forming a seal with the interior surface of conventional barrels.
Accordingly, it is a primary object of the present invention to provide improved methods and apparatus for dispensing compositions.
Another object of the present invention is to provide methods and apparatus for enabling a practitioner to deliver compositions in a highly controlled manner, particularly viscous compositions.
Yet another object of the present invention is to provide syringes having plungers with integral plunger tips adapted to forming a seal with the interior surface of barrels.
Finally, an object of the present invention is to provide syringes which are inexpensive to manufacture.
Additional objects and advantages of the invention are set forth hereinbelow in the detailed description, or will be appreciated by the practice of the invention.
To achieve the foregoing objects, and in accordance with the invention as embodied and broadly described herein, the present invention provides a novel syringe having an a hollow elongated barrel engaged by a plunger having a unique plunger tip.
The barrel has a sidewall extending between a top grasping end and an opposing bottom end. The sidewall has an interior surface which defines a chamber for holding a composition. The barrel also has an opening at the top grasping end for accessing the chamber and an exit port at the bottom end for enabling the composition to exit the chamber. A grasping handle preferably extends perpendicularly and radially from the sidewall at the proximal grasping end of the barrel.
The plunger includes a stem having a round and hollow sidewall extending between a distal lead end ad a proximal pushing end. The side wall of the stem bifurcates at the distal lead end of the plunger into an inset branch and a spring lever. The inset branch extends to an engagement surface such as a face and an evacuator. The area of the plunger defined by the inset branch and the engagement surface is also preferably hollow.
A radial tensioning groove is located at the plunger tip. More particularly, the radial tensioning groove is defined by an exterior wall of the inset branch and an interior wall of the spring lever. The exterior wall of the inset branch is essentially parallel with the longitudinal axis of the plunger means while interior wall of the spring lever is at an angle with respect to the exterior wall of the inset branch. Accordingly, the interior wall of the spring lever and the exterior wall of the inset branch are the sides of the radial tensioning groove. The radial tensioning groove preferably has an angle of about 15xc2x0 before the plunger is inserted into barrel.
The spring lever has an exterior wall with a lower portion which is continuous with the sidewall of the stem. The spring lever also has an upper portion which flares outward at an angle with respect to the lower portion and then terminates at a rounded distal contact end. The angle at which the upper portion of the exterior wall of the spring lever flares outward with respect to the lower portion of the exterior wall of the spring lever is preferably about 10xc2x0.
The spring lever is sufficiently thick from its lower portion up to the distal contact end to enable the spring lever to flex primarily at the base of the radial tensioning groove. Additionally, the spring lever has a thickness which tapers from its lower portion to the rounded distal contact end. More particularly, the spring lever preferably tapers in thickness such that its thickness at the lower portion of the exterior wall is slightly less than the thickness of the sidewall of the stem and its thickness at its distal contact end is about half the thickness of the sidewall of the stem. This thickness helps the spring lever to have the desired flexibility and rigidity. The length of the spring lever relative to its thickness can also affect the desired flexibility and rigidity. The ratio of the length of the spring lever to its thickness at its distal contact end is preferably no greater than about 4:1.
As a result of this configuration, the diameter of the spring lever at the rounded distal contact end is slightly greater than the diameter of the interior surface of the sidewall of the barrel before the plunger is inserted into the barrel. This enables the spring lever to push against the interior surface of the sidewall of the barrel.
The spring lever is sufficiently flexible that upon insertion of the plunger into the chamber of the barrel, the radial tensioning groove compresses due to the spring lever flexing toward the inset branch. The spring lever is also sufficiently rigid to enable the rounded distal contact end to form a seal with the interior surface of the sidewall of the barrel as it is exerted against the interior surface of the sidewall of the barrel.
The above described syringe and method of use provides several advantages and improvements over the prior art. The syringes can be used with any composition, however, such plungers are particularly useful with dental compositions.
These and other objects, features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.